• Bulletin of the Korean Chemical Society
• /
• 제16권2호
• /
• pp.149-153
• /
• 1995

We have grown GaAs epilayers by chemical beam epitaxy(CBE) using unprecracked hydrides and metal organic compounds via a surface decomposition process. This result shows that unprecracked arsine (AsH3) or monoethylarsine (MEAs) can be used in chemical beam epitaxy(CBE) as a replacement of a precracked AsH3 source in CBE. It was also found that the uptake of carbon impurity in epilayers grown using trimethylgallium(TMG) with unprecracked AsH3 or MEAs was significantly reduced compared to that in epilayers grown by CBE process employing TMG and arsenics produced from precracked hydrides. We propose a surface structural model suggesting that the hydrogen atoms play an important role in the reduction of carbon content in GaAs epilayer. Intermediates like dihydrides from hydride sources were also considered to hinder carbon atoms from being incorporated into the epilayers or to remove other carbon containing species on the surface.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 1997년도 한국재료학회 추계학술발표회
• /
• pp.131-131
• /
• 1997

• 공업화학
• /
• 제10권1호
• /
• pp.129-134
• /
• 1999

4차 암모늄염 촉매 존재하에서 poly(glycidyl methacrylate)[poly(GMA)]에 이산화탄소를 직접 부가시켜 poly[(1,3-dioxolane-2-oxo-4-yl)methyl methacrylate][poly(DOMA)]를 합성하였다. 4차 암모늄염 촉매는 높은 이산화탄소 고정화 효율을 나타내었으며, 양이온의 크기가 클수록, 짝음이온의 친핵성이 강할수록 높은 촉매 활성을 나타내었다. 또한 반응온도가 높을수록 높은 이산화탄소 부가율을 나타내었다. 한편 고압 회분 반응기에서 이산화탄소의 압력변화를 관찰함으로써 실시한 속도론적 고찰 결과 반응속도는 poly(GMA)와 이산화탄소의 농도에 대하여 각각 1차 반응이었고, 이때 반응속도상수 k는 $0.69L/mol{\cdot}h$이었다. DMSO를 용매로 사용한 경우 $80^{\circ}C$에서의 $CO_2$의 Henry 상수 H'는 $6.8{\times}10^{-4}mol/L{\cdot}KPa$로 나타났다.

• 한국결정성장학회지
• /
• 제23권6호
• /
• pp.296-301
• /
• 2013

Carbon coils could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under the thermal chemical vapor deposition system. A 304-type stainless steel was used as a substrate with nickel powders as the catalyst. The surface of the substrate was pretreated using a sand paper or a mechanical drill to enhance the production yield of the carbon coils. The characteristics of the deposited carbon nanomaterials on the substrates were investigated according to the surface state on the stainless steel substrate. The protrusion induced by the grooves on the substrate surface could enhance the formation of the carbon nanomaterials having the coils geometries. The cause for the enhancement of the carbon coils formation by the grooves was suggested and discussed with the surface energies for the interaction between as-growing carbon elements. Finally, we could obtain the massive production yield of the carbon coils by the surface pretreatment using SiC sand papers on the several tens grooved stainless steel substrate.

• Advances in nano research
• /
• 제16권4호
• /
• pp.353-363
• /
• 2024

The incorporation of nanoplatelets in composite and polymeric materials represents a recent and innovative approach, holding substantial promise for diverse property enhancements. This study focuses on the application of nanocomposites in the production of sports equipment, particularly soccer balls, aiming to bridge the gap between theoretical advancements and practical implications. Addressing the longstanding challenge of suboptimal interaction between carbon nanofillers and epoxy resin in epoxy composites, this research pioneers inventive solutions. Furthermore, the investigation extends into unexplored territory, examining the integration of glass fiber/epoxy composites with nanoparticles. The incorporation of nanomaterials, specifically expanded graphite and graphene, at a concentration of 25.0% by weight in both the epoxy structure and the composite with glass fibers demonstrates a marked increase in impact resistance compared to their nanomaterial-free counterparts. The research transcends laboratory experiments to explore the practical applications of nanocomposites in the design and production of sports equipment, with a particular emphasis on soccer balls. Analytical techniques such as infrared spectroscopy and scanning electron microscopy are employed to scrutinize the surface chemical structure and morphology of the epoxy nanocomposites. Additionally, an in-depth examination of the thermal, mechanical, viscoelastic, and conductive properties of these materials is conducted. Noteworthy findings include the efficacy of surface modification of carbon nanotubes in preventing accumulation and enhancing their distribution within the epoxy matrix. This optimization results in improved interfacial interactions, heightened thermal stability, superior mechanical properties, and enhanced electrical conductivity in the nanocomposite.

• 한국재료학회지
• /
• 제20권10호
• /
• pp.513-517
• /
• 2010

There have been many efforts to modify and improve the properties of functional thin films by hybridization with nano-sized materials. For the fabrication of electronic circuits, micro-patterning is a commonly used process. For photochemical metal-organic deposition, photoresist and dry etching are not necessary for microscale patterning. We obtained direct-patternable $SnO_2$ thin films using a photosensitive solution containing Ag nanoparticles and/or multi-wall carbon nanotubes (MWNTs). The optical transmittance of direct-patternable $SnO_2$ thin films decreased with introduction of nanomaterials due to optical absorption and optical scattering by Ag nanoparticles and MWNTs, respectively. The crystallinity of the $SnO_2$ thin films was not much affected by an incorporation of Ag nanoparticles and MWNTs. In the case of mixed incorporation with Ag nanoparticles and MWNTs, the sheet resistance of $SnO_2$ thin films decreased relative to incorporation of either single component. Valence band spectral analyses of the nano-hybridized $SnO_2$ thin films showed a relation between band structural change and electrical resistance. Direct-patterning of $SnO_2$ hybrid films with a line-width of 30 ${\mu}m$ was successfully performed without photoresist or dry etching. These results suggest that a micro-patterned system can be simply fabricated, and the electrical properties of $SnO_2$ films can be improved by incorporating Ag nanoparticles and MWNTs.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
• /
• pp.242-243
• /
• 2017

Despite its excellent properties, polyurea coating waterproofing material is exposed to sunlight when it is applied to the exterior wall of concrete by exposed waterproofing method such as a roof of a building, resulting in a problem of causing a large deterioration in performance compared to initial properties. The purpose of this study is to investigate the effect of carbon fiber incorporation on the performance of carbon fiber - reinforced polyureas and to study the optimum carbon fiber length and content respectively. Result of the study confirmed that the performance of the carbon fiber was improved by 2% or more, and the carbon fiber length was 30 ㎛ and the mixing ratio was 3%. It is expected that stable durability can be secured when manufacturing fiber-incorporated polyureas.

• Carbon letters
• /
• 제27권
• /
• pp.72-80
• /
• 2018

In the present work, a comparative study of the mechanical behavior of two series of elastomeric composites, based on carboxylated styrene butadiene rubber (X-SBR) and reinforced with rice bran carbon (RBC) and graphite, is reported. Hybrid composites of X-SBR filled with RBC-graphite were also investigated in terms of the cure characteristics, hardness, tensile properties, abrasion resistance, and swelling. It was observed that the cure times decreased with the incorporation of a carbon filler whereas the torque difference, tensile strength, tensile modulus, hardness, and swelling resistance increased compared to the neat X-SBR revealing a favorable characteristic of crosslinking. Dynamic rheological analysis showed that the G' values of the composites, upon the addition of RBC-graphite, were changed to some extent. This demonstrates that the presence of a strongly developed network of fillers will ensure a reinforcing characteristic in a polymer matrix.

• 한국초전도ㆍ저온공학회논문지
• /
• 제15권2호
• /
• pp.12-15
• /
• 2013

The pure and carbon (C)-doped $MgB_2$ thin films were fabricated on $Al_2O_3$ (0001) substrates at a temperature of $650^{\circ}C$ by using hot-filament-assisted hybrid physical-chemical vapor deposition technique. The $T_c$ value for pure $MgB_2$ film is 38.5 K, while it is between 30 and 35 K for carbon-doped $MgB_2$ films. Expansion in c-axis lattice parameter was observed with increase in carbon doping concentration which is in contrast to carbon-doped $MgB_2$ single crystals. Significant enhancement in the critical current density was obtained for C-doped $MgB_2$ films as compared to the undoped $MgB_2$ film. This enhancement is most probably due to the incorporation of C into $MgB_2$ and the high density of grain boundaries, both help in the pinning of vortices and result in improved superconducting performance.

• 환경영향평가
• /
• 제22권1호
• /
• pp.1-17
• /
• 2013

Carbon sequestration on soil is one of the counter measurements against climate change in agricultural sector. Increasing incorporation of organic fertilizer would increase soil organic carbon (SOC) but it could bring high potential of nutrient losses which would result in water quality degradation. In this paper, literature review on soil organic carbon behavior according to agricultural management is presented. The results of field experiment to identify the effect of organic and commercial fertilizer applications on SOC and runoff water quality were also presented. Field experiment confirmed increased SOC and nutrient concentrations in runoff water as application rate of organic fertilizer increase. The potential use of simulation model to develop best agricultural management practice considering carbon sequestration and water quality conservation at the same time is discussed and monitoring and modeling strategies are also suggested to achieve the goal.